QUANTITATIVE EFFECT OF RELEASERS ON ATTACK READINESS OF FISH HAPLOCHROMIS BURTONI (CICHLIDAE, PISCES)

Observations suggest that the color patterns of Haplochromis burtoni act as primary stimuli in eliciting different responses from a territorial conspecific male. 15 dummies which represented various combinations of form and color patterns of a conspecific male were presented to males in order to determine changes in attack readiness (measured in bites/min) caused by different color patterns. Of all the territorial colorations of a male comprising a distinctive head pattern and body and fin coloration (cf. Fig. 3c), only two components were found to affect the attack readiness: the vertical component of the head pattern and the orange patch above the pectoral fins. The former, if presented without the latter, increased the attack rate by 2.79 bites/min. The latter, if presented without the former, decreased it by 1.77 bites/min. A dummy with both colorations present increased the attack rate by 1.08 bites/min, i.e. the sum of the effect of both components if presented separately (2.79-1.77). It is suggested that these color patterns keep levels of attack readiness within limits amongst territorial males in a colony. Similar explanations may apply to the function of conspicuous color markings in other cichlids. © 1969 Springer-Verlag.